1. Field of the Invention
The present invention relates to a rotary piston machine with a piston arrangement mounted in a gas-tight interior housing. The piston arrangement includes at least four individual rotary pistons which are constructed essentially equally and have end faces which are arranged so as to be in alignment with each other. Each rotary piston is connected to a shaft, wherein the shafts are mounted in the housing so as to be rotatable, wherein the shafts extend through the geometric center axes of the rotary pistons and wherein the shafts are synchronized so as to rotate with each other by means of a gear system. The shafts serve to rotate the rotary pistons in the same direction of rotation about their geometric center axes which extend perpendicularly to the end faces and/or cross-sections of the rotary pistons. The rotary pistons are constructed as straight cylinders whose cross-sections extending parallel to the end faces of the rotary pistons are each defined by four circular arcs with two different radii, wherein the circular arc portions having the same radius also have the same arc lengths, and wherein the circular arc portions are joined alternatingly in connection points where the circular arc portions are connected to each tangentially. The rotary pistons define with their curved circumferential surfaces an inner work chamber, wherein a gap with a periodically changing width is present in each position between adjacent rotary pistons. The rotary piston machine further includes sealing assemblies composed of positioning members and sealing rods, wherein a sealing assembly is provided for each gap between adjacent rotary pistons and wherein each sealing assembly includes at least one sealing rod. The sealing rod has a cross-sectional width which is greater than the width of the gap. The sealing rod is held in its position relative to the gap by means of at least one positioning member which extends between two adjacent rotary pistons. The sealing rod has a length which corresponds at most to the length of the rotary piston.
2. Description of the Related Art
In a known rotary piston machine with sealing assemblies disclosed in U.S. Pat. No. 3,809,026, the rotors have an elliptical cross-section and the sealing assemblies are composed of sealing rods which partially have round cross-sections and which are rigidly connected to each other through a connecting member. As a result of this configuration, generally only one of the two sealing rods of each sealing assembly rests against the outer surfaces of the rotors, while the other sealing rod projects freely and without contact, as shown in FIG. 8 of U.S. Pat. No. 3,809,026. Consequently, the sealing rods are not guided, they move back and forth during operation and must be moved into the sealing position with additional aids, for example, the interior pressure. Another disadvantage is the extraordinary high friction between the rigid sealing rods and the circumferential surfaces of the rotary pistons, wherein each rotary piston is contacted at least twice by the sealing rods.
French Patent 657 191 and EP 0 339 034 B1 disclose rotary piston machines which have similar disadvantages with respect to sealing friction. In the embodiment of French Patent 657 191, increased friction results from internal pressure, centrifugal force and rigid sealing rods in frictional direction. In the embodiment of EP 0 399 034 B1, the increased friction results from the wedge-shaped profile of the rigid sealing rods in connection with the internal pressure.